The intercellular matrix (NtkF) of the marine sponge, Microciona prolifera, is a large proteoglycan that is highly glycosylated, sulfated and contains equal amounts of protein and carbohydrate. There is a protein core from which radiate many arms with a high carbohydrate content. Subunits are linked to each other via carbohydrate-carbohydrate bonds, two epitopes of which have been chemically defined. Hyaluronic acid (HA) is a component of MAF, but until now itsfunctional role has been unclear. We have found that MAR as well as MbA.Fds, have potent inhibitory activity against HIV virally infected lymphoid cells and the inhibitory activity I at levels as low as 0. 1 n-&rograms/ml in the absence of any toxicity. We need to sort out, characterize and compare the components of NLAFds in order to identify those with HIV inhibitory effects. The ones which are anionic, i.e., sulfated disaccharide and sulfated tetrasaccharide, may qualify (there maybe others); since these types of anionic compounds have shown HIV inhibition. If their viral inhibitory activity is based upon charge effects, they may prove useful against other enveloped viruses with protein composition similar to HIV. Our recent studies on sponge have shown that sulfation may be an important modifier of cell functions, such as masking of lectins and modulating reactions between proteoglycans and cell surface receptors. The first batch was M[AFds or lyophilized supernatant derived from ethanolic precipitation of M[AFl (water-dialyzed purified M[AF gel that was lyophilized). The second batch was M[AFl (water-dialyzed and lyophilized purified M[AF gel), which was used to derive M[AFds. The mass spectra and GC retention times indicate five monosaccharides with the following relative abundance: Fuc 14%; Man18%; Gal 32%; GlcU 4.5%; GlcNAc; 31%. Neuraminic acid was checked by a very short time methanolysis and none was detected. The total amount of carbohydrate was calculated to be 3.7% - a very small amount.